(iii) ENGINE PERFORMANCE RESTORATION: in respect of each
 Engine, an amount equal to the Engine Supplemental Rent
 Rate for each Engine Flight Hour (or fraction thereof)
 operated by that Engine during that calendar month
 ("Engine Supplemental Rent"); provided, however, Lessee
 shall have no obligation to make any payment of Engine
 Supplemental Rent in respect of any period

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 during which the Engine installed on the Aircraft is
 subject to a maintenance cost per hour agreement or
 similar arrangement with the Agreed Maintenance
 Performer so long as (x) such agreement or arrangement
 is approved in advance (i.e., before the enrollment of
 the Engine installed on the Aircraft in any such
 agreement or arrangement) in writing by Lessor (such
 approval not to be unreasonably withheld), and (y) in
 the event that the Engine installed on the Aircraft is
 enrolled in any such agreement or arrangement before
 Lessor approves such agreement or arrangement, or in the
 event that any Engine enrolled in any such agreement or
 arrangement is to be installed on the Aircraft before
 Lessor approves such agreement or arrangement, then
 Lessee shall pay and continue to pay Engine Supplemental
 Rent in accordance with this subclause for all periods
 prior to the time at which Lessee obtains Lessor's
 written approval (which approval shall not be
 unreasonably delayed) of the applicable agreement or
 arrangement (if ever);